The marine green alga Chlamydomonas W80 is surprisingly tolerant tooxidative stress, and is potentially applicable to photobiological hydrogenproduction

摘要

A marine green alga Chlamydomonas sp. W80 shows a surprisingly high tolerance tooxidative stress caused by methyl vilologen (MV) and copper ion, while Chlamydomonasreinhardtii, a widely studied model photosynthetic microorganism, is quite sensitive tooxidative stress. When the oxidative stress tolerance was compared with IC50 (inhibitoryconcentration 50%) values, the C. W80 cells show approximately 2,000 times highertolerance to MV (IC50 = 60 microM), and 150 times to copper chloride (IC50 = 1.2 mM), thand℃. reinhardtii cells. The C. W80 has a quite effective H2O2-eliminating enzymes, such asascorbate peroxidase and gluthatione peroxidase (1-3). Some CO2-fixing enzymes,NADP(+)-glyceraldehyde-3-phosphate dehydrogenase and sedoheptulose-1,7-bisphosphatase,were also found to be resistant to H2O2 damege (4). This extremely highoxidative-stress-tolerance of C. W80 must be advantageous for efficient photobiologicalhydrogen production because superoxide and hydrogen peroxide are inevitably generatedwhen the intra-chloroplast condition becomes reductive. Our preliminary studies revealedthat the C. W80 cells evolve hydrogen both under dark anaerobic and light anaerobicconditions, although the hydrogen productivity was quite low.